SOLUTION: The mean lifetime of electric bulb produced by a company has in the past been 1120 hours
with a standard deviation of 125 hours. A sample of 8 electric bulbs recently chosen form
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Question 1083230: The mean lifetime of electric bulb produced by a company has in the past been 1120 hours
with a standard deviation of 125 hours. A sample of 8 electric bulbs recently chosen form a supply
of newly manufactured bulbs showed a mean lifetime of 1070 hours. Test the hypothesis that mean
lifetime of the bulbs has not changed using a level of significance of 0.05.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
Ho=no change
Ha=a change
alpha=0.05 P{reject Ho|Ho true}
test statistic is z
critical value |z|>1.96
calculation z=(x-1120)/s/sqrt(8)
=-50*sqrt(8)/125=0.89
Fail to reject Ho; insufficient evidence exists to say there has been a change.
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